Hurricane Floyd brushed Florida without living up to the worst of its reputation. Still, it was a major storm, bringing with it mighty lashings of rain and gale-force winds. Orlando has seen its like before, and there's nothing we can do about Acts of Nature, right? Wrong, according to the latest scientific thinking.
Hurricanes aren't man-made, but the researchers who peer into the eye of storms say they can be considerably aggravated by global warming. Along with droughts, swarms of locusts, steaming-hot summers and rising sea level, stronger hurricanes are just one more reason to worry about the buildup of carbon dioxide in the Earth's atmosphere.
To understand how carbon loading amps up storm pressures, it's necessary to know how the big blows (about 45 a year around the world) form over the ocean. The basic recipe for a hurricane, according to Discovery Online, is sea water heated to at least 80 degrees Fahrenheit, very humid ambient air, and a moderate storm.
As MIT hurricane researcher Kerry Emanuel describes it, "Winds form into the clouds a few miles above the planet's surface, curving around the storms and forming a ring, like a giant spinning donut. As rain falls into it and evaporates, the spinning donut cools off and starts sinking. The donut pulls the cluster into a spinning storm." When that storm hits the surface of the water, the womb of the hurricane is formed. The taller a storm is and the more ocean heat it contains, the more intense it will be.
So heat has a lot to do with storm intensity. Emanuel's computer models offer a frightening vision of just how bad a super-heated hurricane, or "hypercane" in his colorful phrase, could be. When it comes, a hypercane will make a Category 5 hurricane like 1969's Camille look like a spring rain. The eruption of a giant underwater volcano, for instance, would boil the ocean and produce the mother of all tropical storms, with 500 mile-per-hour winds whipping debris, water vapor and sea spray 20 miles into the stratosphere. Fifty-foot tidal waves would inundate the shoreline, and the ozone layer would be seriously damaged.
It isn't likely that we'll see such a killer storm anytime soon, because it could only be triggered by an event of cosmic proportions. But we should nonetheless batten the hatches for an increasingly bumpy ride. While we may notice only that summers seem to be getting slightly hotter, the energy stored up in greenhouse gas emissions since the Industrial Revolution is remarkably potent, scientists say, adding up to enough heat to light two one-watt Christmas lights over every square meter of the Earth's surface.
According to the prestigious journal Science, global warming is likely to bring more severe weather around the world, and could turn a moderate hurricane with winds of 110 miles per hour into an "extensive" one with blows over 120 mph. And it would take only a two-degree-Centigrade increase in ocean temperature to trigger that kind of increase.
Meteorologists Tom Knutson, Robert Tuleya and Yoshio Kurihara study hurricanes and typhoons for the National Oceanic and Atmospheric Administration (NOAA), and in their 1998 Science article they compared 51 northwest Pacific storms under current conditions with the same events under warmer, high-carbon conditions. The extra 10 mph they found could translate into a great deal of extra destruction. "The damage is usually kind of proportional to the square of the windspeed, so the impact can be quite dramatic," Tuleyo told Reuters. The scientists' computer predictions tend to confirm what were only theoretical estimates a decade ago.
Scientists at the Bermuda Station for Biological Research turn the NOAA predictions on their head: Not only does global warming aggravate storm intensity, they say, but hurricanes also aggravate global warming by reducing the oceans' ability to act as a carbon dioxide "sink." The damage occurs as big storms cool the water and also whip it up into foam, releasing carbon dioxide in the process. The effect, the scientists say, is "rather like shaking up a fizzy drink," and it forces huge amounts of carbon dioxide into the atmosphere, they reported in the journal Nature last year.
The scientists measured carbon dioxide produced by storms in the Sargasso Sea during 1995. The 130-mph winds of Hurricanes Felix, Luis and Marilyn produced carbon dioxide transfers 55 percent above normal, they found.
Chris Landsea of NOAA's Hurricane Research Division in Miami is pessimistic about the storm seasons ahead, though we've enjoyed a relatively calm period since 1969. "It looks like we're heading into a period of more hurricanes that could last for a couple of decades," he says. Scientists say that El Niño's cooling effect helped tamp down storm conditions in the last few years, but water temperatures since 1995 have been running one degree warmer than normal.
But don't worry; be happy. At least that's the way S. Fred Singer, a conservative scientist who specializes in global warming naysaying, sees it. Writing in his book "Hot Talk, Cold Science," he notes blithely that "severe storms, both extra-tropical and tropical, have not increased in the past 50 years." He actually predicts that, even if global warming did occur, its net effect would be to reduce "the driving force for storms and severe weather." But few other scientists support that view, and Singer's professional training was as an astrophysicist.
Singer might have missed the fact that, as Ross Gelbspan reports in his book "The Heat Is On," hurricanes, cyclones and floods in Europe, Asia and North America set the insurance industry back $30 billion a year between 1990 and 1995 -- compared to less than $2 billion a year between 1980 and 1989. In 1996, the worst cyclone of the century killed 2,000 people in Hyderabad, India. Three weeks earlier, another storm there killed 350.
Hurricanes are indeed a natural phenomenon, but that doesn't mean we're powerless to affect them. Every time we drive a sport-utility vehicle or use electricity generated by coal, we're contributing to the "hypercane" of the near future.